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a9a4a7ad56
Author: Andres Freund Reviewed-By: David Steele Discussion: https://postgr.es/m/20200615182235.x7lch5n6kcjq4aue@alap3.anarazel.de
159 lines
5.8 KiB
C
159 lines
5.8 KiB
C
/*-------------------------------------------------------------------------
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*
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* snapmgr.h
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* POSTGRES snapshot manager
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*
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* Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/include/utils/snapmgr.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef SNAPMGR_H
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#define SNAPMGR_H
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#include "access/transam.h"
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#include "utils/relcache.h"
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#include "utils/resowner.h"
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#include "utils/snapshot.h"
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/*
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* The structure used to map times to TransactionId values for the "snapshot
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* too old" feature must have a few entries at the tail to hold old values;
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* otherwise the lookup will often fail and the expected early pruning or
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* vacuum will not usually occur. It is best if this padding is for a number
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* of minutes greater than a thread would normally be stalled, but it's OK if
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* early vacuum opportunities are occasionally missed, so there's no need to
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* use an extreme value or get too fancy. 10 minutes seems plenty.
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*/
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#define OLD_SNAPSHOT_PADDING_ENTRIES 10
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#define OLD_SNAPSHOT_TIME_MAP_ENTRIES (old_snapshot_threshold + OLD_SNAPSHOT_PADDING_ENTRIES)
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/*
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* Common definition of relation properties that allow early pruning/vacuuming
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* when old_snapshot_threshold >= 0.
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*/
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#define RelationAllowsEarlyPruning(rel) \
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( \
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RelationNeedsWAL(rel) \
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&& !IsCatalogRelation(rel) \
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&& !RelationIsAccessibleInLogicalDecoding(rel) \
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)
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#define EarlyPruningEnabled(rel) (old_snapshot_threshold >= 0 && RelationAllowsEarlyPruning(rel))
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/* GUC variables */
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extern PGDLLIMPORT int old_snapshot_threshold;
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extern Size SnapMgrShmemSize(void);
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extern void SnapMgrInit(void);
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extern TimestampTz GetSnapshotCurrentTimestamp(void);
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extern TimestampTz GetOldSnapshotThresholdTimestamp(void);
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extern bool FirstSnapshotSet;
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extern PGDLLIMPORT TransactionId TransactionXmin;
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extern PGDLLIMPORT TransactionId RecentXmin;
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extern PGDLLIMPORT TransactionId RecentGlobalXmin;
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extern PGDLLIMPORT TransactionId RecentGlobalDataXmin;
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/* Variables representing various special snapshot semantics */
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extern PGDLLIMPORT SnapshotData SnapshotSelfData;
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extern PGDLLIMPORT SnapshotData SnapshotAnyData;
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extern PGDLLIMPORT SnapshotData CatalogSnapshotData;
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#define SnapshotSelf (&SnapshotSelfData)
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#define SnapshotAny (&SnapshotAnyData)
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/*
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* We don't provide a static SnapshotDirty variable because it would be
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* non-reentrant. Instead, users of that snapshot type should declare a
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* local variable of type SnapshotData, and initialize it with this macro.
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*/
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#define InitDirtySnapshot(snapshotdata) \
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((snapshotdata).snapshot_type = SNAPSHOT_DIRTY)
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/*
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* Similarly, some initialization is required for a NonVacuumable snapshot.
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* The caller must supply the xmin horizon to use (e.g., RecentGlobalXmin).
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*/
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#define InitNonVacuumableSnapshot(snapshotdata, xmin_horizon) \
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((snapshotdata).snapshot_type = SNAPSHOT_NON_VACUUMABLE, \
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(snapshotdata).xmin = (xmin_horizon))
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/*
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* Similarly, some initialization is required for SnapshotToast. We need
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* to set lsn and whenTaken correctly to support snapshot_too_old.
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*/
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#define InitToastSnapshot(snapshotdata, l, w) \
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((snapshotdata).snapshot_type = SNAPSHOT_TOAST, \
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(snapshotdata).lsn = (l), \
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(snapshotdata).whenTaken = (w))
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/* This macro encodes the knowledge of which snapshots are MVCC-safe */
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#define IsMVCCSnapshot(snapshot) \
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((snapshot)->snapshot_type == SNAPSHOT_MVCC || \
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(snapshot)->snapshot_type == SNAPSHOT_HISTORIC_MVCC)
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extern Snapshot GetTransactionSnapshot(void);
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extern Snapshot GetLatestSnapshot(void);
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extern void SnapshotSetCommandId(CommandId curcid);
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extern Snapshot GetOldestSnapshot(void);
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extern Snapshot GetCatalogSnapshot(Oid relid);
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extern Snapshot GetNonHistoricCatalogSnapshot(Oid relid);
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extern void InvalidateCatalogSnapshot(void);
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extern void InvalidateCatalogSnapshotConditionally(void);
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extern void PushActiveSnapshot(Snapshot snapshot);
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extern void PushCopiedSnapshot(Snapshot snapshot);
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extern void UpdateActiveSnapshotCommandId(void);
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extern void PopActiveSnapshot(void);
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extern Snapshot GetActiveSnapshot(void);
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extern bool ActiveSnapshotSet(void);
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extern Snapshot RegisterSnapshot(Snapshot snapshot);
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extern void UnregisterSnapshot(Snapshot snapshot);
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extern Snapshot RegisterSnapshotOnOwner(Snapshot snapshot, ResourceOwner owner);
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extern void UnregisterSnapshotFromOwner(Snapshot snapshot, ResourceOwner owner);
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extern FullTransactionId GetFullRecentGlobalXmin(void);
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extern void AtSubCommit_Snapshot(int level);
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extern void AtSubAbort_Snapshot(int level);
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extern void AtEOXact_Snapshot(bool isCommit, bool resetXmin);
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extern void ImportSnapshot(const char *idstr);
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extern bool XactHasExportedSnapshots(void);
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extern void DeleteAllExportedSnapshotFiles(void);
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extern bool ThereAreNoPriorRegisteredSnapshots(void);
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extern TransactionId TransactionIdLimitedForOldSnapshots(TransactionId recentXmin,
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Relation relation);
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extern void MaintainOldSnapshotTimeMapping(TimestampTz whenTaken,
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TransactionId xmin);
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extern char *ExportSnapshot(Snapshot snapshot);
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/*
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* Utility functions for implementing visibility routines in table AMs.
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*/
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extern bool XidInMVCCSnapshot(TransactionId xid, Snapshot snapshot);
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/* Support for catalog timetravel for logical decoding */
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struct HTAB;
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extern struct HTAB *HistoricSnapshotGetTupleCids(void);
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extern void SetupHistoricSnapshot(Snapshot snapshot_now, struct HTAB *tuplecids);
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extern void TeardownHistoricSnapshot(bool is_error);
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extern bool HistoricSnapshotActive(void);
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extern Size EstimateSnapshotSpace(Snapshot snapshot);
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extern void SerializeSnapshot(Snapshot snapshot, char *start_address);
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extern Snapshot RestoreSnapshot(char *start_address);
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extern void RestoreTransactionSnapshot(Snapshot snapshot, void *source_pgproc);
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#endif /* SNAPMGR_H */
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